1. Field of the Invention
The invention relates to a driver circuit for discharge lamps and a method for operating same.
2. Discussion of the Background of the Invention and Material Information
European Patent Publication EP 146 683 describes a ballast or driver for discharge lamps where the inverter is switched off when a lamp is found to be permanently inoperative. After switching off the inverter, a DC-current flows through the lamp circuit, and since this current flows through a heating cathode of each lamp, it drops to zero as soon as a lamp is removed. This makes it possible to detect a lamp replacement by monitoring the current, such that the inverter can be restarted automatically once a lamp has been replaced.
This method has the disadvantage that it only monitors one of the electrodes of each lamp. Furthermore, it is not well suited for use in circuits in which the heating current is coupled inductively into the electrodes.